Syrian rebel commander Ahmad Mihbzt and his ragtag fighters grabbed their aging rifles to fight Syrian troops advancing on their village, but soon fled under a rain of exploding artillery shells.

GORENTAS, Turkey — Syrian rebel commander Ahmad Mihbzt and his ragtag fighters grabbed their aging rifles to fight Syrian troops advancing on their village, but soon fled under a rain of exploding artillery shells.

“We will fight until our last drop of blood,” Mihbzt declared a week later in this village across the Turkish border. “We just withdrew because we ran out of ammunition.”

Like Mihbzt’s men, rebels across Syria fighting to topple President Bashar Assad lack the weapons that can pose a serious challenge to the regime’s large, professional army. Some rebel units have more fighters than guns, forcing them to take turns fighting. Because of ammunition shortages, some fire automatic rifles one shot at a time, counting each bullet.

Rebel leaders and anti-regime activists say rising gun prices and more tightly controlled borders are making it harder for them to acquire arms and smuggle them into Syria. This could tip the already unbalanced military equation of Syria’s year-old uprising further in the regime’s favor.

The opposition has suffered a series of military setbacks as regime forces have repeatedly routed them in their strongholds, most recently the eastern city of Deir al-Zour on Tuesday.

The weapons shortage has grown so acute that the opposition’s disorganized leadership say only military aid can stop Assad’s forces. Saudi Arabia, Qatar and Libya have spoken positively of the idea, but no country is known to be arming the rebels. The United States and many European countries have rejected sending weapons, fearing that it would fuel a civil war.

The weapons problems reflect the fractured, haphazard nature of the rebel movement. The uprising began a year ago with peaceful protests demanding political reform, inspired by the successful revolts in Tunisia and Egypt. Since then, Assad has waged a withering crackdown.

In response, some in the opposition began to take up arms to defend their towns and attack government troops. The local militias and breakaway units from the Syrian army mostly identify with the Free Syrian Army, a loose-knit umbrella group, but they operate independent of each other. The groups, numbering anywhere from a few dozen to a few hundred men, are largely on their own in finding weapons and supplies.

• Tim Johnson, MCT Campus